Tightening the requirements for species diagnoses would help integrate DNA-based descriptions in taxonomic practice.

Modern advances in DNA sequencing hold the promise of facilitating descriptions of new organisms at ever finer precision but have come with challenges as the major Codes of bionomenclature contain poorly defined requirements for species and subspecies diagnoses (henceforth, species diagnoses), which is particularly problematic for DNA-based taxonomy. We, the commissioners of the International Commission on Zoological Nomenclature, advocate a tightening of the definition of "species diagnosis" in future editions of Codes of bionomenclature, for example, through the introduction of requirements for specific information on the character states of differentiating traits in comparison with similar species. Such new provisions would enhance taxonomic standards and ensure that all diagnoses, including DNA-based ones, contain adequate taxonomic context. Our recommendations are intended to spur discussion among biologists, as broad community consensus is critical ahead of the implementation of new editions of the International Code of Zoological Nomenclature and other Codes of bionomenclature.

Indonesian species of Dilatognathus Kluge 2012 (Ephemeroptera, Leptophlebiidae, Choroterpes s.l.) and species-specific sexual dimorphism in development of maxilla.

Larvae, subimagoes and imagoes of both sexes reared from larvae of a new species Choroterpes (Dilatognathus) bogori sp.n. from Java are described. Formerly this species was described by Ulmer (1939) under the wrong name "Choroterpides exiguus (Eaton 1884)". In all species of Dilatognathus, maxilla of last instar larva has the same structure, but in Ch. (D.) cataractae its structure is different in previous instars, being different in males and females. 

New subgenus and new species Nousia (Araucophlebia) latifolia subgen. n. et sp. n. (Ephemeroptera: Leptophlebiidae) from Chile.

A new subgenus and new species, Nousia (Araucophlebia) latifolia subgen. et sp.n., are described from the Maule and Araucania regions in Chile, based on male and female imagos reared from larvae. This species has unusual shapes of larval tergalii, male imaginal genitalia and flat eggs.

New Oriental tribe Iscini, new non-dilatognathan species of Notophlebia Peters & Edmunds 1970 and independent origin of Dilatognathus-type mouth apparatus in Atalophlebiinae (Ephemeroptera: Leptophlebiidae).

A new tribe, Iscini tr. n., comprising the Oriental genera Isca Gillies 1951 and Notophlebia Peters & Edmunds 1970, is established. A new species, Notophlebia ganeshi sp. n., is described based on male and female imagos reared from larvae. The new species markedly differs from N. jobi Sivaramakrishnan & Peters 1984 by its non-specialized larval mouth apparatus. The larva of N. jobi has a highly specialized mouth apparatus of the «Dilatognathus-type¼; this type of mouth apparatus has evolved independently in several non-related leptophlebiid taxa.

A new species, Procloeon monilistylus sp. n. (Ephemeroptera, Baetidae), from the Russian Far East.

A new, two-winged species Procloeon monilistylus sp. n. is described from the Russian Far East based on male and female imagoes reared from larvae. The larva differs from other species of Procloeon by having a deeply separated incisor and kinetodontium of the mandibles. The imago differs from all Baetidae (and mayflies in general) by the shape of the gonostyli. Formerly this species was known as "Cloeon (Centroptilum) sp. 1" sensu Kluge & Novikova 1992.

Redescriptions of Indian species of Nigrobaetis Kazlauskas (in Novikova & Kluge) 1987 (Ephemeroptera, Baetidae).

The European species Nigrobaetis gracilis (Bogoescu & Tabacaru 1957) and more than 19 Asian and African species of Nigrobaetis Kazlauskas (in Novikova & Kluge) 1987 belong to the subgenus Margobaetis Kang & Yang 1994, which is characterized by peculiar asymmetric eggs and narrow paraglossa of larval labium. A new synonymy is established: Nigrobaetis (Margobaetis) minutus (Mller-Liebenau 1984) = N. paramakalyani Kubendran & Balasubramanian in Kubendran et al. 2015 = N. sumbensis Kaltenbach & Gattolliat 2023, synn.n.; winged stages (male and female imagines and subimagines) and eggs of this species are described for the first time. N. (M.) minutus is widely distributed on Oriental Region, being revealed in West Malaysia, Southern India, Sumba and Sulawesi islands in Indonesia. Winged stages (male and female imagines and subimagines) and eggs of Nigrobaetis (Margobaetis) klugei Sivaruban et al. 2022 are described for the first time.

Mayflies of the genus Nonnullidens Grant & Peters 1993 (Ephemeroptera: Leptophlebiidae) from New Guinea.

In light of the discovery of four new species of Leptophlebiidae (Ephemeroptera) from the Indonesian part ofNew Guinea, the generic name Barba Grant & Peters 1993 syn.n. is regarded here to be a junior synonym of Nonnullidens Grant & Peters 1993. Nonnullidens variegatus sp. n., N. niger sp. n. and N. reductus sp. n. are described from larvae, subimagoes and imagoes, with the stages associated by rearing. Nonnullidens depapricus sp. n. is described from an immature male larva of the last instar. Nonnullidens mariae comb.n. formerly known only from eastern New Guinea, is reported from the Baliem Valley.

Mayflies of the Caucasus Mountains. II. Description of the first representative of the subgenus Helvetoraeticus Bauernfeind & Soldán, 2012 (Heptageniidae: Ecdyonurus).

The first representative of the subgenus Helvetoraeticus Bauernfeind & Soldán, 2012, from the Caucasus Mountains, Ecdyonurus (Helvetoraeticus) adjaricus sp. nov., is described on the basis of larvae, female imago (reared from larva) and male imago from the Autonomous Republic of Adjara, Georgia. The male imago of the new species can be separated from other representatives of Helvetoraeticus by its conspicuous yellowish wings coloration (especially of hind wings) and the shape of the penis lobes. The larva has a distinctive broad and apically pointed lateral projection on the pronotum, pointed bristles on the ventral side of the posterior border of the femora and markedly long, sharp posterolateral expansions of abdominal sterna. This last character is unique within Helvetoraeticus. The new species is most closely related to E. krueperi (Stein, 1863).

Reclassification of Teloganodes Eaton 1882 (including subgenera Dudgeodes Sartori 2008 and Derlethina Sartori 2008) with a new species from Sulawesi (Ephemeroptera, Teloganodidae).

The genera Teloganodes Eaton 1882 sensu Sartori et al. 2008 and Dudgeodes Sartori 2008 in the original sense, were artificial taxa, and the genus Derlethina Sartori 2008 differed from them only by greater reduction of posterior tergalii. In the present paper, the genus Teloganodes is accepted in wide sense and includes the 3 following formal subgenera: (1) subgenus Teloganodes, stat. n. (= Macafertiella Wang in Wang & McCafferty 1996) contains only species with 5 pairs of tergalii (i.e. tergalii II-VI); (2) subgenus Dudgeodes Sartori in Sartori et al. 2008, stat. n. contains all species with 4 pairs of tergalii (i.e. tergalii II-V); (3) subgenus Derlethina Sartori in Sartori et al. 2008, stat. n. contains species with 3 pairs of tergalii (i.e. tergalii II-IV). The species Teloganodes jacobusi Sartori in Sartori et al. 2008 and T. hubbardi Sartori in Sartori et al. 2008 are moved to the subgenus Dudgeodes. The following new combinations are established: Teloganodes (Dudgeodes) hutanis (Sartori in Sartori et al. 2008) comb. n.; T. (D.) stephani (Sartori in Sartori et al. 2008) comb. n.; T. (D.) ulmeri (Sartori in Sartori et al. 2008) comb. n.; T. (D.) pescadori (Sartori in Sartori et al. 2008) comb. n.; T. (D.) celebensis (Sartori in Sartori et al. 2008) comb. n.; T. (D.) palnius (Selvakumar et al. in Selvakumar et al. 2014) comb. n.; T. (D.) bharathidasani (Anbalagan in Anbalagan et al. 2015) comb. n.; T. (D.) romani (Martynov et al. 2016) comb. n.; T. (D.) bauernfeindi (Garces & Sartori in Garces et al. 2020) comb. n.; T. (D.) freitagi (Garces & Sartori in Garces et al. 2020) comb. n.; T. (D.) luntian (Garces & Sartori in Garces et al. 2020) comb. n.; T. (D.) pangantihoni (Garces & Sartori in Garces et al. 2020) comb. n.; T. (D.) tabang (Garces & Sartori in Garces et al. 2020) comb. n.; T. (D.) vonrinteleni (Garces & Sartori in Garces et al. 2020) comb. n.; T. (D.) sartorii (Srinivasan et al. 2021) comb. n.; T. (D.) molinerii (Sivaruban et al. in Martynov et al. 2022) comb. n.; T. (D.) selvakumari (Martynov & Palatov in Martynov et al. 2022) comb. n.; T. (Derlethina) eloisae (Sartori in Sartori et al. 2008) comb. n.; T. (Derlethina) tamiraparaniae (Selvakumar et al. in Selvakumar et al. 2014) comb. n. Larvae, subimagines, imagines of both sexes and eggs of T. (D.) celebensis are described; a new species, T. (D.) rasus sp. n. is described from Sulawesi based on male imago and subimago reared from larva.

Redescription of the subgenus Securiops Jacobus, McCafferty & Gattolliat 2006 (Ephemeroptera, Baetidae, Procloeon Bengtsson 1915).

The taxon Securiops Jacobus, McCafferty& Gattolliat 2006 is treated here as a subgenus of the genus Procloeon Bengtsson 1915; it shares all characters of Procloeon s.l. and besides them, has peculiar autapomorphies in mouthparts structure. Diagnoses of Cloeon/fg1 (or the tribe Cloeonini sensu Kluge 2016), Procloeon/g1 (or the genus Procloeon sensu Kluge 2016) and Securiops are given. Larvae of the South African species Procloeon (Securiops) falcatum (Crass 1947) comb. n. are described for the first time. Based on reared specimens from Zambia, larvae of Procloeon (Securiops) macafertiorum Lugo-Ortiz (in Lugo-Ortiz & McCafferty) 1996 are redescribed; subimagines, imagines and eggs of this species are described for the first time. New larval characters of Procloeon (Securiops) mutadens (Jacobus et al. 2006) comb. n. are reported based on a larva from Gambia. Based on reared specimens from Thailand, larvae of Procloeon (Securiops) primasia (Kaltenbach et al. 2023) comb. n. are redescribed; subimagines, imagines and well-developed eggs of this species are described for the first time. Genitalia of Cheleocloeon excisum (Barnard 1932) are figured for the first time.

A new, widespread genus of Baetidae from South Asia (Insecta, Ephemeroptera).

Material collected on different islands across South Asia revealed a new genus of Baetidae with a widespread distribution, Arcobaetisgen. nov. The larvae present important similarities with Nigrobaetis, but have paraglossae dorsally with an arc of long, spine-like setae in distal area; long, slightly feathered setae between prostheca and mola of both mandibles; and very slender legs with row of short setae at dorsal margin of femur. The male imago has an extraordinarily small 3rd (apical) segment of gonostylus, which is much narrower than the apex of the 2nd segment. The new genus includes five species: A.sumbawensissp. nov. is described from Sumbawa (Indonesia) based on larvae, A.sumatrensissp. nov. from Sumatra (Indonesia) based on larvae, A.bornensissp. nov. from Borneo (Brunei) based on larvae, and A.sripadaisp. nov. (type species) is described from Sri Lanka based on a reared male imago with its larval and subimaginal exuviae; A.gracilentus (Chang & Yang, 1994), comb. nov. from Taiwan, formerly described in Margobaetis Kang & Yang, 1994, a subgenus of Baetis Leach, 1815, and subsequently transferred to the genus Nigrobaetis Kazlauskas (in Novikova & Kluge), 1987, is transferred to the new genus. A key to the larvae of all species is provided. Morphological similarities and the relationship of the new genus to other genera of Baetidae are discussed.

Indian species of Teloganodes Eaton 1882 (including subgenera Dudgeodes Sartori 2008 and Derlethina Sartori 2008) (Ephemeroptera, Teloganodidae).

According to the classification proposed in the previous publication by Kluge, the genus Teloganodes Eaton 1882 is divided into three subgenera distinguished only by tergalii number: the subgenus Teloganodes (with 5 pairs of tergalii on uromeres II-VI), the subgenus Dudgeodes Sartori in Sartori et al. 2008 (with 4 pairs of tergalii on uromeres II-V) and the subgenus Derlethina Sartori in Sartori et al. 2008 (with 3 pairs of tergalii on uromeres II-IV). All three subgenera are represented in Southern India. Based on the new material, additional descriptions are given to the following species: T. (Teloganodes) kodai Sartori in Sartori et al. 2008 (= Teloganodes barathyae Sivaruban et al. in Martynov et al. 2022, syn. n.); Teloganodes (Teloganodes) dentatus Navás 1932 (= T. sartorii Selvakumar et al. in Selvakumar et al. 2014, syn. n.); Teloganodes (Dudgeodes) palnius (Selvakumar et al. in Selvakumar et al. 2014) (= Dudgeodes bharathidasani Anbalagan et al. 2015, syn. n.; = Dudgeodes sartorii Srinivasan et al. 2021, syn. n.; = Dudgeodes molinerii Sivaruban et al. in Martynov et al. 2022, syn. n.); Teloganodes (Derlethina) tamiraparaniae (Selvakumar et al. in Selvakumar et al. 2014). A new species T. (Teloganodes) velutinus sp. n. is described from the Western Ghats based on larvae, female imagines reared from larvae and eggs.

Diagnosis, variability, distribution and systematic position of Labiobaetis pulchellus (Müller-Liebenau & Hubbard 1985) (Ephemeroptera, Baetidae, Baetis s. l.).

A new synonymy to Labiobaetis pulchellus (Müller-Liebenau & Hubbard, 1985) (= L. soldani Kubendran et al. 2014, syn. n.) is established based on examination of imagines reared from larvae in India and Sri Lanka. This species belongs to the tricolor group, which comprises Holarctic species L. tricolor (Tshernova, 1928), L. propinquus (Walsh, 1863), L. calcaratus (Keffermüller, 1972), and some Oriental species.

Redescription of the subgenus Rhithrogeniella Ulmer 1939 (Ephemeroptera, Heptageniidae, genus Ecdyonurus) based on reared specimens from India and Thailand.

Rhithrogeniella Ulmer 1939 is treated here as a subgenus of the genus Ecdyonurus Eaton 1868 (s. l.). The subgeneric name Rhithrogeniella is a senior synonym of Afghanurus Demoulin 1964 syn. n., Paracinygmula Bajkova 1975 syn. n. and Nixe Flowers 1980 syn. n. Additional description of Ecdyonurus (Rhithrogeniella) ornatus (Ulmer 1939) is given based on imagines and subimagines of both sexes reared from larvae in India and Thailand; lectotype of this species name is designated. Synonymy of E. (Rh.) ornatus and E. (Rh.) tonkinensis Soldán & Braasch 1986 is established (syn. n.). Male and female imagines and subimagines of an unnamed species of Rhithrogeniella are reported from India.

Contribution to the knowledge of the subgenus Tenuibaetis Kang & Yang 1994 (Ephemeroptera, Baetidae, Baetis s. l.).

The taxon Tenuibaetis Kang & Yang (in Kang, Chang & Yang) 1994 is accepted here as a subgenus of the genus Baetis Leach 1815, but not as a genus. In connection with this, new combinations are established: Baetis (Tenuibaetis) parvipterus (Fujitani et al. 2011) comb. n., Baetis (Tenuibaetis) fujitanii (Kaltenbach & Gattolliat 2019) comb. n., Baetis (Tenuibaetis) himani (Kubendran et al. in Kubendran et al. 2022) comb. n., Baetis (Tenuibaetis) kangi (Kubendran et al. in Kubendran et al. 2022) comb. n. and Baetis (Tenuibaetis) panhai (Suttinun et al. 2022) comb. n. Based on reared material, imagines of both sexes and larvae of Baetis (Tenuibaetis) ursinus Kazlauskas 1963, Baetis (Tenuibaetis) hissaricus Novikova 1991, Baetis (Tenuibaetis) frequentus Müller-Liebenau & Hubbard 1985 (= Indobaetis michaelohubbardi Selva-kumar et al. 2012, syn. n.) and B. (T.) fujitanii are redescribed. B. (T.) panhai is redescribed based on subimago reared from larva. Two new species from Southern India, Baetis (Tenuibaetis) kaltenbachi sp. n. and Baetis (Tenuibaetis) bialatus sp. n. are described based on imagines reared from larvae. A new species from Thailand, Baetis (Tenuibaetis) octomaculatus sp. n. is described based on imagines reared from larvae.

Two new species of Waynokiops Hill et al. 2010 (Ephemeroptera: Baetidae) from the Oriental Region.

A new species found in northern Thailand and northern India, Waynokiops pentacanthus sp. n., is described based on eggs, larvae, subimagines and imagines of both sexes associated by rearing. A new species from southern India, Waynokiops palifer sp. n. is described based on a mature larva with female subimago and eggs extracted from this larva. All larvae of both species were collected in rivers running in mountain areas. Formerly, the genus Waynokiops Hill et al. 2010 included a single species W. dentatogriphus Hill et al. 2010 known from a few larvae collected in lakes of North America and unknown before 2007. Based on the fact that two newly discovered species of Waynokiops have an Oriental distribution, an assumption is expressed, that W. dentatogriphus is also originally distributed somewhere in the Oriental Region, from where it was introduced into North America. Winged stages are described for Waynokiops for the first time, allowing a more complete generic diagnosis and a better understanding of its systematic position.

Taxonomic significance of microlepides on subimaginal tarsi of Ephemeroptera.

In each mayfly individual, the surface of the subimaginal cuticle significantly differs both from imaginal and larval cuticles, being different on different parts of the body. Most of the subimaginal body, including femora and tibiae, is covered with microtrichia. Tarsal segments are either also covered with microtrichia, or their microtrichia are transformed into microlepides of various shapes. The most usual forms of microlepides are the pointed and the blunt ones. Arrangements of microtrichia, pointed microlepides, blunt microlepides and other forms of microlepides on certain tarsomeres represent good taxonomic characters, which in some cases allow characterization of high level taxa, and in some cases distinguish closely related species. Arrangement of microlepides and microtrichia on subimaginal tarsi of examined mayfly species is given. The following new synonyms are proposed: Afroptilum boettgeri (Kopelke 1980) = Xyrodromeus africanus Lugo-Ortiz McCafferty 1997, syn. n.; Labiobaetis vinosus (Barnard 1932) = L. tenuicrinitus (Kopelke 1980), syn. n.; Baetis parvulus Crass 1947 = Baetis permultus Kopelke 1980, syn. n.; Epeorus gilliesi Braasch 1981 = Epeorus petersi Sivaruban et al. 2013, syn. n.; Dicercomyzon femorale Demoulin 1954 = Dicercomyzon costale Kimmins 1957, syn. n.

A widespread new genus of Baetidae (Baetidae, Ephemeroptera) from Southeast Asia.

A reinvestigation of type and other material of Baetisjavanicus Ulmer, 1913 and Baetissabahensis Müller-Liebenau, 1984, together with new material from Southeast Asia revealed a new genus, Branchiobaetis gen. nov. The above species are formally assigned to the new genus Branchiobaetis gen. nov. It is characterized by the presence of accessory gills ventrally near fore coxa and at the base of maxillae, a peculiar folding of the gonostyli developing under the cuticle of last instar male larvae, together with a unique combination of other larval characters. Besides the two formerly described species, five new species are identified using a combination of morphology and molecular characters (COI, Kimura 2-parameter distances), four species from Sumatra and one from the Philippines. They are described and illustrated at the larval stage. Additionally, a complementary description of larva and adult stages of the generic type species B.javanicus comb. nov. as well as the first description of the eggs are provided. Furthermore, new reports of B.javanicus comb. nov. and B.sabahensis comb. nov. are indicated. The distribution of Branchiobaetis gen. nov. includes the Indonesian Sunda Islands, Borneo, and the Philippines. A key to the larval stage of all species is provided.

Review of the Kimminsula-complex (Ephemeroptera, Leptophlebiidae).

Distribution of the Kimminsula complex is limited by mountains of the Western Ghats in India and the Central Highlands in Sri Lanka. Indian taxa include the new genus Ghatula gen. n. with 2 new species, Ghatula rufa sp. n. (type species of Ghatula, described here from larvae of both sexes, female subimago, female imago and eggs associated by rearing) and Ghatula quadrimaculata sp. n. (described here from larvae of both sexes); and the genus Petersula Sivaramakrishnan 1984 with type species Petersula courtallensis Sivaramakrishnan 1984 (additionally described here from larvae of both sexes, female subimagines, female imagines and eggs associated by rearing), Petersula heptagenoides sp. n. (described here from larvae, subimagines, imagines of both sexes and eggs associated by rearing) and Petersula nathani Sivaramakrishnan & Hubbard 1984 (known as a single male imago). In Sri Lanka the Kimminsula complex is represented by the following taxa: the new genus Ceylonula gen. n. with the single species Ceylonula femoralis (Hagen 1858) comb. n. (originally in Potamanthus; redescribed here from larvae, subimagines, imagines of both sexes and eggs associated by rearing); the genus Kimminsula Peters & Edmunds 1970 with type species Kimminsula taprobanes (Walker 1853) [= Kimminsula annulata (Hagen 1858)] (redescribed here from larvae, subimagines, imagines of both sexes and eggs associated by rearing), Kimminsula fasciata (Hagen 1858) (redescribed here from larvae, subimagines, imagines of both sexes and eggs associated by rearing), Kimminsula podi sp. n. (described here from larvae, male subimagines, male imagines and eggs associated by rearing) and Kimminsula latifolia sp. n. (described here from larvae); a form intermediate between K. fasciata and K. taprobanes is described here from larvae, subimagines, imagines of both sexes and eggs associated by rearing; and the new genus Hubbardula gen. n. with the single species Hubbardula heterolepida sp. n. (described here from larvae, subimagines, imagines of both sexes and eggs associated by rearing). Systematic position of the Kimminsula-complex is discussed.

First report of Cheleocloeon Wuillot & Gillies 1993 (Ephemeroptera: Baetidae) from the Oriental Region.

A new species, Cheleocloeon vaigaiensis sp. n., is described from Southern India based on larvae, imagines and subimagines of both sexes associated by rearing. This new Oriental species is most closely related to the Afrotropical species Cheleocloeon clavifolium Kluge 2016. Formerly, the genus Cheleocloeon Wuillot & Gillies 1993 was known only from Africa, Madagascar and Arabia; this is the first report of this genus from the Oriental Region.